It is common practice to provide a water opening outside the hull of a marine vessel with a conduit passing through the hull so that cooling water and the like can enter. It is also common practice to provide a scoop to use forward motion of the vessel to facilitate entry of the water and to provide a strainer as part of the scoop. The purpose of the strainer is to keep objects and marine life from entering the cooling system. Generally speaking, while the strainer and through-hull fitting can take various forms, the strainer is likely to be dimensioned so that objects larger than about 1/8 inch across will be excluded. An example of an intake strainer of this general type is shown in U.S. Pat No. 3,878,807, Reskusic et al.
However, very small forms of marine life can still enter and, while they do not present a serious problem for the cooling systems, it is common for them to congregate near the entry of the through-hull fitting. In particular, barnacles, mussels and the like tend to attach themselves to the strainer as well as the entry area of the pipe and then grow, ultimately reducing the flow to unacceptable levels.
When this happens, it is necessary to remove the strainer and scoop and to dean the pipe leading through the hull. Such strainers are normally attached to a wood or fiberglass hull using threaded fasteners which thread directly into the hull, as shown in Reskusic et al. Unfortunately, after several times of removing the strainer, cleaning it and then replacing the strainer, the internal threads in the hull have deteriorated so much that the fasteners no longer hold. It is then necessary to take more drastic steps to replace the fasteners with larger ones or change to a different type of fastener system, neither of these solutions being very good ones.
The basic strainer-cleaning problem has been recognized for some time and efforts have been made to arrive at solutions which obviate the need to remove and replace fasteners in the hull material. An example of this is shown by U.S. Pat. No. 4,809,632, Hamel in which a drawer is built into the strainer. When the strainer becomes dogged with marine life, the objective of Hamel is to allow removal of the strainer which can then be cleaned and replaced. However, Hamel does not provide a complete solution because the shell of the scoop strainer blocks direct access to the through-hull tube. Since it is essential to be able to dean the interior of that tube as well as the strainer itself, the structure of Hamel is insufficient. In addition, it does not appear that the drawer system of Hamel would be very practical in a real marine environment because the sliding components thereof and the small components would not appear to stay in working order very long. A more practical system is therefore still needed.